Method and system for controlling a turbocharged two stroke engine based on boost error

Abstract

A method and system for controlling a wastegate comprises determining a boost pressure target, measuring a boost pressure, determining a boost pressure error from the measured boost pressure and the boost pressure target, determining a wastegate position change based on boost pressure error, and changing the wastegate position corresponding to the wastegate position change.

What is claimed: 
     
       1. A method of controlling a wastegate comprising:
 generating a vehicle speed signal corresponding to a vehicle speed; 
 determining a throttle position sensor signal corresponding to a throttle position; 
 determining a boost set point based on the throttle position sensor signal; 
 receiving a selection signal from a user interface comprising at least one of a multiple position switch, a touch screen, and a button, the selection signal corresponding to one of a plurality of different boost modes, said user interface separate from the throttle position sensor; 
 determining a boost mode scale factor based on the selection signal from the user interface; 
 when the throttle position is opened above a predetermined position or when the vehicle speed is greater than a predetermined speed, determining a boost pressure target based on the boost set point and not the boost mode scale factor; 
 when the throttle position is opened less than the predetermined position or when the vehicle speed is less than the predetermined speed, determining the boost pressure target based on the boost mode scale factor and the boost set point; 
 measuring a boost pressure to obtain a measured boost pressure; 
 determining a boost pressure error from the measured boost pressure and the boost pressure target; 
 determining a wastegate position change based on the boost pressure error; and 
 changing the wastegate position corresponding to the wastegate position change. 
 
     
     
       2. The method of  claim 1 , wherein when the boost pressure error is greater than a threshold, generating more change in the position of the wastegate than when the boost pressure error is less than the threshold. 
     
     
       3. The method of  claim 1 , wherein when a difference between the measured boost pressure and the boost pressure target is greater than a threshold, generating different change in the position of the wastegate than when the difference is less than the threshold. 
     
     
       4. The method of  claim 1 , wherein when a difference between the measured boost pressure and the boost pressure target is greater than a threshold, generating more change in the position of the wastegate than when the difference is less than the threshold. 
     
     
       5. The method of  claim 1 , wherein determining the wastegate position change comprises determining the wastegate position change based on a lookup table. 
     
     
       6. The method of  claim 1 , wherein determining the boost pressure error comprises determining the boost pressure error by subtracting the measured boost pressure from the boost pressure target. 
     
     
       7. The method of  claim 1 , wherein determining the boost pressure target comprises determining the boost pressure target in response to an engine speed and the throttle position. 
     
     
       8. The method of  claim 1 , wherein determining the boost pressure target comprises determining the boost pressure target in response to an engine speed, the throttle position, and barometric pressure. 
     
     
       9. A system comprising:
 a throttle position sensor generating a throttle position signal corresponding to a throttle position; 
 a vehicle speed sensor generating a vehicle speed signal corresponding to a vehicle speed; 
 a boost set point module coupled to the throttle position sensor and generating a boost set point; 
 a user selectable interface generating a selection signal corresponding to one of a plurality of different boost modes, said user interface separate from the throttle position sensor; 
 a boost pressure sensor generating a measured boost pressure signal; 
 a controller programmed to determine a boost mode scale factor from the selection signal, determine a boost pressure error from the boost pressure signal and a boost pressure target, and determine a wastegate position change based on the boost pressure error, said boost pressure target based on the boost pressure set point and not the boost mode scale factor when the throttle position is opened above a predetermined position or when the vehicle speed is greater than a predetermined speed, said boost pressure target based on the boost mode scale factor and the boost pressure set point when the throttle position is opened less than the predetermined position or when the vehicle speed is less than the predetermined speed; and 
 a wastegate actuator coupled to the controller changing a position of a wastegate based on the wastegate position change. 
 
     
     
       10. The system of  claim 9 , wherein the controller is programmed to generate more change in the position of the wastegate when the boost pressure error is greater than a threshold. 
     
     
       11. The system of  claim 9 , wherein the controller is programmed to generate a different wastegate position change when the boost pressure error is greater than a threshold versus when the boost pressure error is less than the threshold. 
     
     
       12. The system of  claim 9 , wherein the controller is programmed to generate less change in the position of the wastegate when the boost pressure error is less than a threshold. 
     
     
       13. The system of  claim 9 , wherein the controller is programmed to determine the wastegate position change based on a lookup table. 
     
     
       14. The system of  claim 9 , wherein the controller is programmed to determine the boost pressure error comprises determining the boost pressure error by subtracting the boost pressure target from the measured boost pressure signal. 
     
     
       15. The system of  claim 9 , wherein the controller is programmed to determine the boost pressure target in response to an engine speed and the throttle position. 
     
     
       16. The system of  claim 9 , wherein the controller is programmed to determine the boost pressure target in response to an engine speed, the throttle position, and barometric pressure.